1. Field of the Invention
The present invention relates to a passive auxiliary condensing apparatus of a nuclear power plant, and more particularly to a passive auxiliary condensing apparatus, which is an auxiliary feedwater system for cooling a nuclear core of a nuclear power plant in an event of an accident.
2. Description of the Related Art
An auxiliary feedwater system is provided in a nuclear power plant to ensure safety in operating a nuclear reactor.
Such auxiliary feedwater system includes a passive auxiliary feedwater system (PAFS), which is a well known passive auxiliary cooling system in which a steam pipe is connected to outlet of a steam generator and the steam pipe is configured to pass through a cooling water tank, which is separately provided, to condense a steam outputting from the steam pipe, thereby supplying a feedwater.
Meanwhile, a prior art emergency core cooling system is disclosed in Korea Patent Publication No. 2002-0037105, which is published May 18, 2002.
In order to secure safety in the nuclear power plant, a method of cooling a secondary system of the nuclear reactor may be used.
However, such conventional cooling system is of an active type, which can be operated only by an electricity supply. Thus, the conventional cooling system has a problem such that it cannot be operated when an accident occurs in which the electricity supply is interrupted.
In order to solve the above described problem, as shown in FIG. 1, a conventional passive auxiliary feedwater system (PAFS) 10 includes a steam generator 30 connected to a reactor vessel 20 and a cooling tank 50 including a heat exchanger 40 installed therein, wherein the heat exchanger 40 is connected to the steam generator 30.
A steam outputted from an upper portion of the steam generator 30 is introduced to the heat exchanger 40 and passes through the cooling tank 50 so that the steam is condensed so that a water liquid returns to a lower portion of the steam generator 30.
However, in the conventional passive feedwater system 10 described above, a water, which is generated by the steam passing through the heat exchanger 40 and the cooling tank 50 and is recovered by the steam generator 30 is not a 100% liquid water but is a mixture of a water and steam. Therefore, a vibration can be caused during when the mixture of the water and steam is re-introduced to the steam generator 30 and a shock wave can be generated during when a remaining steam is condensed into the water, thereby damaging the system. Also, a quality of a cooling water re-introduced into the steam generator 30 can be lowered.